The driver escaped with injuries that were described by police as non-life-threatening.
Witnesses said the driver hit a concrete barrier on the Ile-aux-Tourtes Bridge before losing control of the vehicle and dropping into the Lake of Two Mountains while still inside the truck.
Provincial police say two fishermen pulled the 36-year-old from the vehicle.
The man was transported to hospital, where he remained as of Friday afternoon.
Police said they planned to question the man when he is ready to meet them.
Jean-Francois Page, head of the company that employs the man and owns the tractor-trailer, said in a statement it's too early to determine what happened.
He added the company, Transport Herve Lemieux, would conduct its own investigation.
Employees of Quebec's Transport Department were dispatched to analyze the bridge to ensure it didn't suffer structural damage.
Attempts to lift the vehicle out of the water are set to begin Saturday morning.